The present invention relates to an improved apparatus and method for preserving organs for organ transplantation. More particularly, the present invention relates to an apparatus and method that maintains the organ at optimal temperatures ex vivo until reperfusion, thereby preventing external warming of the organ and ischemic injury, and thereby improving graft performance and survival.
Over the past 45 years, great strides have been made in organ transplantation. Improved organ preservation techniques, solutions, and apparatus have made it possible to preserve organs hours to days after removal of the organs from the donor body, thereby allowing for transportation of donor organs to recipients at great distances away.
One current technique for preserving a donor organ involves core cooling the organ to 4xc2x0 C. in situ with preservation solution just prior to removal from a donor cadaver. Cooling the organ to 4xc2x0 C. results in hypothermic cellular metabolic arrest, wherein the organ is in a non-functioning state. The organ is then stored for transport on ice or in a preservation chamber that maintains the organ at approximately 4xc2x0 C. and in a metabolically inactive state. Once an organ arrives at its ultimate destination, and the recipient has been prepared, the organ is removed from ice or the preservation chamber and sewn into place in the recipient. This method is described in, for example, U.S. Pat. No. 3,810,367. While this method allows for the transport of donor organs, there are drawbacks. During the period when the organ is xe2x80x9cout of icexe2x80x9d, prior to reperfusion (e.g. liver 40 to 90 minutes, kidney 25 to 60 minutes, pancreas 25 to 60 minutes), the organ begins to warm up, from the outside toward the center, due to exposure to a combination of ambient (22xc2x0 C.) and recipient body temperature (37xc2x0 C.). As a result, the organ returns to its functioning metabolic demands. However, since the organ is not yet connected to the recipient""s blood supply and can not receive metabolic substrate, ischemic injury ensues leading to the death of cells, functional components of the tissue, and the liberation of toxic substances. This injury recapitulates what occurs in tissue deprived of oxygen usually due to obstruction of the arterial blood supply or inadequate blood flow leading to hypoxia in the tissue. Ischemia results in irreversible damage to the organs. The process of xe2x80x9cout of icexe2x80x9d warming is particularly injurious to the kidney due to the fact that the outer region of the kidney, called the cortex, contains the most important functional elements and this outer area is exposed to the most rapid increase in temperature and ischemic injury. Prolonged xe2x80x9cout of icexe2x80x9d time has been associated with poor long-term function and an increased incidence of primary nonfunction of kidney, heart, liver, lung and pancreas allografts.
Recently, techniques and apparatus have been used which maintain the donor organ in an in vivo-like state during transport. Such techniques and apparatus are described in, for example, U.S. Pat. Nos. 6,046,046, 6,100,082, and 5,586,438 which describe, generally, an apparatus that provides a continuous flow of perfusate to the organ. These apparatus may further include a reduced temperature preservation chamber for holding and maintaining the organ at a reduced temperature. However, these techniques and apparatus require that the organ be disconnected from the perfusion apparatus and removed from the reduced temperature preservation chamber while the organ is placed into the recipient""s body and sewn into place. This results in warming and ischemia.
It is often difficult to predict which organs will take longer to implant and, thus, it would be advantageous to externally cool all organs until they are sewn into place in the recipient""s body to prevent this warming up process. Further, the relationship between tissue injury and time xe2x80x9cout of icexe2x80x9d appears to be linear. Thus, because warm ischemia produces a graded injury, reducing the xe2x80x9cout of icexe2x80x9d time to essentially zero would result in significant theoretical benefits in preserving the functional units of the organs.
The present invention provides an apparatus and method for ex vivo preservation of donor organs prior to implantation in a recipient body. More particularly, the apparatus and method of the present invention maintains a donor organ at a reduced temperature while the organ is sewn into place in the recipient""s body (i.e. until reperfusion). By maintaining the organ at a suitable reduced temperature, the potential for warming and ischemia are reduced.
When used herein, a xe2x80x9creduced temperaturexe2x80x9d refers to a temperature below room temperature that can minimize ischemic damage to an organ, preferably a temperature approaching 4xc2x0 C., such as below about 10xc2x0 C. or 15xc2x0 C., more preferably within about 1, 2 or 3xc2x0 C. of 4xc2x0 C.
An exemplary embodiment of the apparatus includes a sleeve or blanket for receiving a donor organ and a temperature controlling mechanism for regulating the temperature of the sleeve or blanket. The donor organ is wrapped in the temperature regulated sleeve or blanket, which, in turn, maintains the organ at a desired temperature. Various temperature controlling mechanisms are well-known and, thus, although described below with reference to a preferred embodiment, the general features of the temperature controlling mechanism may be in accordance with conventional temperature controlling mechanisms.
The sleeve or blanket is preferably sufficiently non-rigid to envelope and directly contact multiple surfaces of the three-dimensional organ. Thus, the sleeve or blanket can be wrapped around the three-dimensional organ. Less preferred, although within the scope of the invention, is a more rigid sleeve or blanket that may not contact multiple organ surfaces.
In one embodiment, the temperature controlling mechanism comprises circulating fluid, which regulates the temperature of the sleeve or blanket. In specific embodiments, the sleeve or blanket has an internal pathway for the circulation of cooling fluid. Cooling fluid enters the sleeve or blanket through an entrance port in the sleeve or blanket, flows through the internal pathway, and then exits the sleeve or blanket through an exit port. In one embodiment, the cooling fluid is maintained in a reservoir and a pump circulates the fluid through the internal pathway of the sleeve or blanket. The fluid may be disposed of or returned to the reservoir for recirculation through the sleeve or blanket. The circulating fluid may be cooled within the reservoir or, in some embodiments, a cooling mechanism may be located in the pathway from the reservoir to the entrance port to cool the fluid prior to entering the sleeve or blanket. In some embodiments heating fluid may be circulated through the sleeve or pad rather than or in addition to cooling fluid. In such an embodiment, the fluid may be heated within the reservoir or heated prior to entering the sleeve or blanket.
A method for maintaining donor organ at optimal temperatures until reperfusion is also disclosed. The method comprises providing an apparatus having a donor organ receiving portion and a temperature controlling mechanism for regulating the temperature of donor organ receiving portion. More particularly, the method comprises removing a donor organ from a donor body and transporting the donor organ to the operating site using conventional means. For example, the organ for transplantation may first be core cooled to 4xc2x0 C. in situ with preservation solution just prior to removal from a donor, thereby inducing hypothermic metabolic arrest. The non-functioning organ is then placed in a preservation container that maintains the organ at approximately 4xc2x0 C. while the organ is transported to the operating site. Once an organ has arrived at the operating site, the recipient is prepared and the organ is removed from the storage container. The organ is then immediately placed in the donor organ receiving portion of the present apparatus with the vascular pedicle of the organ protruding from the apparatus. A temperature controlling mechanism maintains the organ receiving portion at a temperature of hypothermic metabolic arrest, which maintains the temperature of the donor organ at a temperature of hypothermic metabolic arrest while the organ is sewn into place in the recipient and while the vascular pedicle is connected to the recipient""s blood vessels. By maintaining the organ at a temperature of hypothermic arrest during implantation and until reperfusion, the potential for warming of the organ and ischemic damage is reduced.
The apparatus of the invention may provide beneficial effects for a range or organs, including solids organs of the human chest and abdominal regions, such as for use in connection with the transplant of a kidney, liver, lung, heart or pancreas. The cooling apparatus of the invention also will be useful for the transplant of other organs such as appendages e.g. human hand, foot, or finger. As referred to herein, the term appendages is inclusive of hands, feet, fingers, toes, etc.
Other aspects and embodiments of the invention are discussed infra.